<?xml version='1.0' encoding='UTF-8'?>

   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       targetNamespace='urn:ietf:params:xml:ns:xmpp-tls'
       xmlns='urn:ietf:params:xml:ns:xmpp-tls'
       elementFormDefault='qualified'>

     <xs:element name='starttls'>
       <xs:complexType>
         <xs:choice minOccurs='0' maxOccurs='1'>
           <xs:element name='required' type='empty'/>
         </xs:choice>
       </xs:complexType>
     </xs:element>

     <xs:element name='proceed' type='empty'/>

     <xs:element name='failure' type='empty'/>

     <xs:simpleType name='empty'>
       <xs:restriction base='xs:string'>
         <xs:enumeration value=''/>
       </xs:restriction>
     </xs:simpleType>

   </xs:schema>